Flow cytometry has become a key and critical research tool with applications in a wide range of disciplines in basic research, clinical translational research, and clinical studies. A wealth of reagents to identify specific cell sub-population, to study molecules regulating cell proliferation, apoptosis, signal transduction pathways, and functional states in cells are now available. Further, the fluorescent dyes and labeling techniques are now available to permit the simultaneous detection of many of these molecules and markers in individual cells. This is leading to the need for increasingly complex cytometric assays to understand the role and interaction of these molecules at the cell level. The Flow Cytometry Core Facility of the Robert H. Lurie Comprehensive Cancer Center at Northwestern University serves over 59 investigators with national peer reviewed funding of $22,631,071. This facility has a strong history of close, active interaction with its user base facilitating implementation of more difficult flow cytometry assays by all investigators regardless of their level of expertise. This coupled with the increase in available reagents has fostered increasingly complex requests of the facility. At present, the facility has a bench top analyzer, a Beckman-Coulter XLMLC four color instrument and a Beckman-Coulter ELITE ESP cell sorter which is over six years old. The current cell sorter has distinct limitations in the areas of complex, multi-laser and high speed sorting applications. Key for the Flow Cytometry Core Facility to meet the current and future needs of our user base is development of more complex and sophisticated multi-parameter and high-speed sorting capabilities. The requested MoFlo(TM) instrumentation will facilitate this critical development. This development will be aided by the MoFlo's enhanced multi-laser capabilities (three separate laser interrogation spots, focused/pinhole collection for all fluorescence detectors) and high speed sorting capabilities (25,000-50,000 cells/sec, 10-15X our current instrument capabilities). Further, the facilities oversight by Director, Dr. Charles Goolsby, with over 23 years experience in research and clinical flow cytometry and Mary Paniagua MT(ASCP)SI, with over 12 years experience in flow cytometry ensure that efficient implementation of these enhanced capabilities will occur.